Secreted Proteases from Dermatophytes
- 748 Downloads
Dermatophytes are highly specialized pathogenic fungi that exclusively infect the stratum corneum, nails or hair, and it is evident that secreted proteolytic activity is important for their virulence. Endo- and exoproteases-secreted by dermatophytes are similar to those of species of the genus Aspergillus. However, in contrast to Aspergillus spp., dermatophyte-secreted endoproteases are multiple and are members of two large protein families, the subtilisins (serine proteases) and the fungalysins (metalloproteases). In addition, dermatophytes excrete sulphite as a reducing agent. In the presence of sulphite, disulphide bounds of the keratin substrate are directly cleaved to cysteine and S-sulphocysteine, and reduced proteins become accessible for further digestion by various endo- and exoproteases secreted by the fungi. Sulphitolysis is likely to be an essential step in the digestion of compact keratinized tissues which precedes the action of all proteases.
KeywordsAspergillus Dermatophytes Microsporum Secreted proteases Trichophyton
Phenyl methyl sulphonyl fluoride
We thank Dr. Sandy Vermout, Dr. Peter Staib and Dr. Massimo Lurati for their critical review of the manuscript and assistance with the English. This work was supported by the Swiss National Foundation for Scientific Research, grant 3100-105313/1.
- 2.Barrett AJ, Rawlings ND, Woessner JF, editors. Handbook of proteolytic enzymes. 2nd ed. London: Elsevier; 2004.Google Scholar
- 8.Mignon B, Swinnen M, Bouchara JP, Hofinger M, Nikkels A, Pierard G, Gerday C, Losson B. Purification and characterization of a 31.5 kDa keratinolytic subtilisin-like serine protease from Microsporum canis and evidence of its secretion in naturally infected cats. Med Mycol. 1998;36:395–404.PubMedGoogle Scholar
- 16.Asahi M, Lindquist R, Fukuyama K, Apodaca G, Epstein WL, McKerrow JH. Purification and characterization of major extracellular proteinases from Trichophyton rubrum. Biochem J. 1989;232:139–44.Google Scholar
- 27.Hamaguchi T, Morishita N, Usui R, Takiuchi I. Characterization of an extracellular keratinase from Microsporum canis. Jpn J Med Mycol. 2000;41:257–62.Google Scholar
- 29.Simon M, Green H. Enzymatic cross-linking of involucrin and other proteins by keratinocytes particulates in vitro. Cell. 1985;40:687–3.Google Scholar
- 50.Kunert J. Physiology of keratinophilic fungi. In: Kushwaha RKS, Guarro J, editors. Biology of dermatophytes and other keratinophilic fungi. Bilbao: Revista Iberoamericana de Micología; 2000. p. 77–85.Google Scholar